1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display (LCD) device, and a method of driving the same.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field. The LCD device using twisted nematic (TN) liquid crystal is referred to as a TN mode LCD device.
However, the TN mode LCD device has narrow viewing angles. To resolve this problem, an in-plane switching (IPS) mode LCD device is suggested.
FIG. 1 is a schematic view illustrating an IPS mode LCD device according to the related art.
Referring to FIG. 1, a liquid crystal panel 20 of the LCD device 10 includes gate lines GL1 to GL3 in a row direction, data lines DL1 to DL3 in a column direction, and common lines CL1 to CL3 in the row direction.
Pixels P are arranged in a matrix form and are connected to the corresponding gate, data and common lines GL1 to GL3, DL1 to DL3 and CL1 to CL3. The pixel P includes a switching transistor T, a liquid crystal capacitor Clc and a storage capacitor Cst. The switching transistor T is connected to the corresponding gate and data lines GL1, GL2 or GL3 and DL1, DL2 or DL3. The liquid crystal capacitor Clc and the storage capacitor Cst are connected to the switching transistor T. The liquid crystal capacitor Clc includes a pixel electrode, a common electrode, and a liquid crystal layer between the pixel and common electrodes. The pixel and common electrodes are formed in the same substrate, for example, an array substrate to induce an in-plane electric field, and thus liquid crystal molecules of the liquid crystal layer are driven by the in-plane electric field. The switching transistor T is formed in the array substrate where the pixel and common electrodes are formed. The storage capacitor Cst includes first and second storage electrodes.
The pixel electrode of the liquid crystal capacitor Clc and the first electrode of the storage capacitor Cst are connected to the switching transistor T. The common electrode of the liquid crystal capacitor Clc and the second electrode of the storage capacitor Cst are connected to the corresponding common line CL1, CL2 or CL3 to be supplied with a common voltage. The common lines CL1 to CL3 are connected together thus supplies the same common voltage to all the pixels P of the liquid crystal panel 20.
Gate voltage, for example, turn-on gate voltages are sequentially supplied to the gate lines GL1 to GL3. When the gate voltage is supplied, the switching transistor T of the pixel P connected to the corresponding gate line GL1, GL2 or GL3 is turned on and a data voltage is supplied to the pixel P through the corresponding data line DL1, DL2 or DL3. The data voltage is supplied to the pixel electrode and thus induces the in-plane electric field along with the common voltage of the common electrode.
The LCD device 10 is operated in an inversion driving method of alternating negative and positive polarities for the pixel P. The inversion driving method is categorized into a dot inversion method, a line inversion method, a frame inversion method and the like. Among these methods, the dot inversion method is widely used.
The dot inversion method is to invert a polarity of the pixel P per pixel and per frame. In other words, neighboring pixels have opposite polarities, and each pixel has opposite polarities per frame. The dot inversion method has advantage of preventing flicker and crosstalk more effectively than other inversion methods.
FIG. 2 is a view illustrating waveform of a data voltage and a common voltage of the LCD device operated in a dot inversion method according to the related art.
Referring to FIG. 2, a common voltage Vcom are maintained at a predetermined level. A data voltage Vdata applied to a pixel changes in polarity with respect to the common voltage Vcom per frame F. For example, the data voltage Vdata has a negative polarity for a frame while the data voltage Vdata has a positive polarity for a next frame, and this polarity inversion is repeated.
However, since the data voltage Vdata applied to the pixel swings with respect to the common voltage Vcom of the constant voltage level, the swing width of the data voltage Vdata is great. This causes increase of power consumption of the LCD device.